1. Field of the Invention
The present invention relates to a polyesterification method, particularly to a polyesterification method under the catalysis of a tin catalyst, which is highly active and capable of accelerating the production of polymers.
2. Description of the Related Art
Generally, metal catalysts such as aluminum, titanium, lithium, or tin are widely used in industries to catalyze the processes of esterification and polyesterification, so that the processes of esterification and polyesterification can be performed in a time-saving process.
Tin catalysts, such as stannous(II) 2-ethylhexanoate, stannous sulfate, stannous dichloride, and dibutyltin oxide, are commonly used in catalysis of a ring-opening polymerization so as to obtain polymers in a high efficiency. Frankly, the activity of the tin catalysts is low, and therefore, the catalysis of the tin catalysts only can be well performed under long term of high temperature. Accordingly, it is wasteful in used of time and energy for the production of polymers, which may burden the industry with heavy cost.
In Taiwan Patent No. TW200301273 entitled “METHYLTIN CATALYSTS FOR POLYESTERFICATION,” a conventional catalyst, being a methyltin compound, for polyesterfication is disclosed, and which can be used as a catalyst in esterfication or polyesterfication under high temperature. With the performance of the methyltin compound, the esters and polyesters produced by the process possess superior physical properties and chemical properties, such as high quality of color, thermal stability and purity. The conventional catalyst is suitable to be used in multistages of polyesterification reactions, and which is quiet frugal in catalyst use.
However, the conventional catalyst, methyltin compound, still has to be performed at a high temperature, for example high than 200° C., and therefore, a significant amount of energy is necessary for the production of polymers as usual. In this way, the polyesterification of industries only can be achieved in an energy-and-cost wasting process yet.
Moreover, the said conventional catalyst is sensitive to air, being easy to react with oxygen and steam in air, with the result that the activity of the conventional catalyst is decreased. Hence, the conventional catalyst not only cannot improve the disadvantages of the tin catalysts in catalysis of polyesterification, but leads to much more amounts of energy and cost in use.
It is suggested that, there is an urgent need of providing a method of polyesterification, which can effectively improve the disadvantages of the conventional arts and dramatically promote the efficiency of the tin catalyst in polyesterification process.